Yarn storage drums have been proposed in which a number of elongated yarn contact or support elements are arranged evenly around the circumference at equal radial distances from the drum axis; the elements extend essentially in the direction of the drum axis and are fastend at least at one end to a drum body. In the yarn contact section they form a yarn contact for several loops or turns of a storage winding. The arrangement also has yarn feeding and delivery elements assigned to the feeding and delivery side of the storage drum, and a drive arrangement to provide of relative rotational movement between the yarn drum, and the winding and unwinding elements.
Yarn delivery arrangements are known (see German Pat. No. 24 61 746) whose storage drum is designed in the form of a cylindrical bar cage on whose bars a yarn coming from a supply spool can be wound tangentially, thus forming the storage winding. The bars are located at some radial distance from the hub portion of the cylindrical body. The body has an upper and a lower circular flange in which the ends of the bars are secured. Each loop or turn of the storage winding theoretically contacts the circularly cylindrical rigid bar at a contact point. The spaces between each bar and the hub portion of the drum body effectively prevent the accumulation of lint which would impair the function of the yarn delivery arrangement. Such a storage drum designed as a solid bar cage is relatively heavy, i.e. it possesses a considerable inert mass. That is of minor importance as long as the storage drum is driven--as a rule jointly with the storage drums of other yarn delivery devices such as those belonging to a circular knitting machine--via an endless belt coupled with a drive source. Generally this belt drive cannot be stopped or started suddenly, and a stop-and-go operation of the storage drum is possible only when the storage drum is designed with its own interengaging clutch that can be engaged and disengaged. Because of its inert mass, the storage drum cannot immediately come to a standstill even when the clutch is disengaged. This would be desirable, however, for example, in circular knitting machines operating with striping attachments, as well as in some other applications. Furthermore such a yarn delivery arrangement is still relatively complicated to design.
The same considerations apply essentially to other similar yarn delivery arrangements (see German Pat. Nos. OS 28 08 203, PS 16 35 899) where the elongated yarn contact elements are separately designed as bar or cog-like parts of an appropriately slotted mantle of a pot-shaped drum body.
Since the yarn contact elements of the storage drums of such delivery arrangements are designed as straight bars, teeth, or etc., separate advance elements are required around which the continuously forming storage windings advance axially along the storage drum, so that the yarn loops or turns of the storage winding are always held in a predetermined yarn contact section. In this respect it is known to design the storage drum with radially protruding fingers or stirrup-like elements, extending, between the individual parallel straight bars that form the yarn contact elements. The protruding finger or stirrup-like elements form elements that can be cam-controlled and perform a limited axial up-and-down motion, pushing the storage winding forward along the yarn contact elements. In one known arrangement of this kind (see German Pat. No. OS 27 23 210) the advance elements are formed by elastic wire pieces protruding radially outward on one side of the drum body, whose one end is fastened to a hub of the drum body and whose other end engages in a hub-like cam travel arranged on a fixed ring surrounding the rotating storage drum at a distance. Another arrangement of this kind (see German Pat. No. OS 31 04 516) has a triangularly bent part and partition elements that protrude radially between the bars that form the yarn contact elements; the partition bars divide the storage winding and resemble wire stirrups whose one end is fastened to a yarn advance element that is cam-controlled and moves axially back and forth on two adjacent yarn contact elements.